1 //===-- CodeGen/AsmPrinter/Win64Exception.cpp - Dwarf Exception Impl ------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file contains support for writing Win64 exception info into asm files.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "Win64Exception.h"
15 #include "llvm/ADT/SmallString.h"
16 #include "llvm/ADT/StringExtras.h"
17 #include "llvm/ADT/Twine.h"
18 #include "llvm/CodeGen/AsmPrinter.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineModuleInfo.h"
22 #include "llvm/CodeGen/WinEHFuncInfo.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/Mangler.h"
25 #include "llvm/IR/Module.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCSection.h"
30 #include "llvm/MC/MCStreamer.h"
31 #include "llvm/MC/MCSymbol.h"
32 #include "llvm/Support/Dwarf.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/FormattedStream.h"
35 #include "llvm/Target/TargetFrameLowering.h"
36 #include "llvm/Target/TargetLoweringObjectFile.h"
37 #include "llvm/Target/TargetOptions.h"
38 #include "llvm/Target/TargetRegisterInfo.h"
39 using namespace llvm;
40
Win64Exception(AsmPrinter * A)41 Win64Exception::Win64Exception(AsmPrinter *A)
42 : EHStreamer(A), shouldEmitPersonality(false), shouldEmitLSDA(false),
43 shouldEmitMoves(false) {}
44
~Win64Exception()45 Win64Exception::~Win64Exception() {}
46
47 /// endModule - Emit all exception information that should come after the
48 /// content.
endModule()49 void Win64Exception::endModule() {
50 }
51
beginFunction(const MachineFunction * MF)52 void Win64Exception::beginFunction(const MachineFunction *MF) {
53 shouldEmitMoves = shouldEmitPersonality = shouldEmitLSDA = false;
54
55 // If any landing pads survive, we need an EH table.
56 bool hasLandingPads = !MMI->getLandingPads().empty();
57
58 shouldEmitMoves = Asm->needsSEHMoves();
59
60 const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
61 unsigned PerEncoding = TLOF.getPersonalityEncoding();
62 const Function *Per = MF->getMMI().getPersonality();
63
64 shouldEmitPersonality = hasLandingPads &&
65 PerEncoding != dwarf::DW_EH_PE_omit && Per;
66
67 unsigned LSDAEncoding = TLOF.getLSDAEncoding();
68 shouldEmitLSDA = shouldEmitPersonality &&
69 LSDAEncoding != dwarf::DW_EH_PE_omit;
70
71
72 // If this was an outlined handler, we need to define the label corresponding
73 // to the offset of the parent frame relative to the stack pointer after the
74 // prologue.
75 const Function *F = MF->getFunction();
76 const Function *ParentF = MMI->getWinEHParent(F);
77 if (F != ParentF) {
78 WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
79 auto I = FuncInfo.CatchHandlerParentFrameObjOffset.find(F);
80 if (I != FuncInfo.CatchHandlerParentFrameObjOffset.end()) {
81 MCSymbol *HandlerTypeParentFrameOffset =
82 Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
83 GlobalValue::getRealLinkageName(F->getName()));
84
85 // Emit a symbol assignment.
86 Asm->OutStreamer.EmitAssignment(
87 HandlerTypeParentFrameOffset,
88 MCConstantExpr::Create(I->second, Asm->OutContext));
89 }
90 }
91
92 if (!shouldEmitPersonality && !shouldEmitMoves)
93 return;
94
95 Asm->OutStreamer.EmitWinCFIStartProc(Asm->CurrentFnSym);
96
97 if (!shouldEmitPersonality)
98 return;
99
100 const MCSymbol *PersHandlerSym =
101 TLOF.getCFIPersonalitySymbol(Per, *Asm->Mang, Asm->TM, MMI);
102 Asm->OutStreamer.EmitWinEHHandler(PersHandlerSym, true, true);
103 }
104
105 /// endFunction - Gather and emit post-function exception information.
106 ///
endFunction(const MachineFunction * MF)107 void Win64Exception::endFunction(const MachineFunction *MF) {
108 if (!shouldEmitPersonality && !shouldEmitMoves)
109 return;
110
111 EHPersonality Per = MMI->getPersonalityType();
112
113 // Get rid of any dead landing pads if we're not using a Windows EH scheme. In
114 // Windows EH schemes, the landing pad is not actually reachable. It only
115 // exists so that we can emit the right table data.
116 if (!isMSVCEHPersonality(Per))
117 MMI->TidyLandingPads();
118
119 if (shouldEmitPersonality) {
120 Asm->OutStreamer.PushSection();
121
122 // Emit an UNWIND_INFO struct describing the prologue.
123 Asm->OutStreamer.EmitWinEHHandlerData();
124
125 // Emit the tables appropriate to the personality function in use. If we
126 // don't recognize the personality, assume it uses an Itanium-style LSDA.
127 if (Per == EHPersonality::MSVC_Win64SEH)
128 emitCSpecificHandlerTable();
129 else if (Per == EHPersonality::MSVC_CXX)
130 emitCXXFrameHandler3Table(MF);
131 else
132 emitExceptionTable();
133
134 Asm->OutStreamer.PopSection();
135 }
136 Asm->OutStreamer.EmitWinCFIEndProc();
137 }
138
createImageRel32(const MCSymbol * Value)139 const MCExpr *Win64Exception::createImageRel32(const MCSymbol *Value) {
140 if (!Value)
141 return MCConstantExpr::Create(0, Asm->OutContext);
142 return MCSymbolRefExpr::Create(Value, MCSymbolRefExpr::VK_COFF_IMGREL32,
143 Asm->OutContext);
144 }
145
createImageRel32(const GlobalValue * GV)146 const MCExpr *Win64Exception::createImageRel32(const GlobalValue *GV) {
147 if (!GV)
148 return MCConstantExpr::Create(0, Asm->OutContext);
149 return createImageRel32(Asm->getSymbol(GV));
150 }
151
152 /// Emit the language-specific data that __C_specific_handler expects. This
153 /// handler lives in the x64 Microsoft C runtime and allows catching or cleaning
154 /// up after faults with __try, __except, and __finally. The typeinfo values
155 /// are not really RTTI data, but pointers to filter functions that return an
156 /// integer (1, 0, or -1) indicating how to handle the exception. For __finally
157 /// blocks and other cleanups, the landing pad label is zero, and the filter
158 /// function is actually a cleanup handler with the same prototype. A catch-all
159 /// entry is modeled with a null filter function field and a non-zero landing
160 /// pad label.
161 ///
162 /// Possible filter function return values:
163 /// EXCEPTION_EXECUTE_HANDLER (1):
164 /// Jump to the landing pad label after cleanups.
165 /// EXCEPTION_CONTINUE_SEARCH (0):
166 /// Continue searching this table or continue unwinding.
167 /// EXCEPTION_CONTINUE_EXECUTION (-1):
168 /// Resume execution at the trapping PC.
169 ///
170 /// Inferred table structure:
171 /// struct Table {
172 /// int NumEntries;
173 /// struct Entry {
174 /// imagerel32 LabelStart;
175 /// imagerel32 LabelEnd;
176 /// imagerel32 FilterOrFinally; // One means catch-all.
177 /// imagerel32 LabelLPad; // Zero means __finally.
178 /// } Entries[NumEntries];
179 /// };
emitCSpecificHandlerTable()180 void Win64Exception::emitCSpecificHandlerTable() {
181 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
182
183 // Simplifying assumptions for first implementation:
184 // - Cleanups are not implemented.
185 // - Filters are not implemented.
186
187 // The Itanium LSDA table sorts similar landing pads together to simplify the
188 // actions table, but we don't need that.
189 SmallVector<const LandingPadInfo *, 64> LandingPads;
190 LandingPads.reserve(PadInfos.size());
191 for (const auto &LP : PadInfos)
192 LandingPads.push_back(&LP);
193
194 // Compute label ranges for call sites as we would for the Itanium LSDA, but
195 // use an all zero action table because we aren't using these actions.
196 SmallVector<unsigned, 64> FirstActions;
197 FirstActions.resize(LandingPads.size());
198 SmallVector<CallSiteEntry, 64> CallSites;
199 computeCallSiteTable(CallSites, LandingPads, FirstActions);
200
201 MCSymbol *EHFuncBeginSym = Asm->getFunctionBegin();
202 MCSymbol *EHFuncEndSym = Asm->getFunctionEnd();
203
204 // Emit the number of table entries.
205 unsigned NumEntries = 0;
206 for (const CallSiteEntry &CSE : CallSites) {
207 if (!CSE.LPad)
208 continue; // Ignore gaps.
209 for (int Selector : CSE.LPad->TypeIds) {
210 // Ignore C++ filter clauses in SEH.
211 // FIXME: Implement cleanup clauses.
212 if (isCatchEHSelector(Selector))
213 ++NumEntries;
214 }
215 }
216 Asm->OutStreamer.EmitIntValue(NumEntries, 4);
217
218 // Emit the four-label records for each call site entry. The table has to be
219 // sorted in layout order, and the call sites should already be sorted.
220 for (const CallSiteEntry &CSE : CallSites) {
221 // Ignore gaps. Unlike the Itanium model, unwinding through a frame without
222 // an EH table entry will propagate the exception rather than terminating
223 // the program.
224 if (!CSE.LPad)
225 continue;
226 const LandingPadInfo *LPad = CSE.LPad;
227
228 // Compute the label range. We may reuse the function begin and end labels
229 // rather than forming new ones.
230 const MCExpr *Begin =
231 createImageRel32(CSE.BeginLabel ? CSE.BeginLabel : EHFuncBeginSym);
232 const MCExpr *End;
233 if (CSE.EndLabel) {
234 // The interval is half-open, so we have to add one to include the return
235 // address of the last invoke in the range.
236 End = MCBinaryExpr::CreateAdd(createImageRel32(CSE.EndLabel),
237 MCConstantExpr::Create(1, Asm->OutContext),
238 Asm->OutContext);
239 } else {
240 End = createImageRel32(EHFuncEndSym);
241 }
242
243 // These aren't really type info globals, they are actually pointers to
244 // filter functions ordered by selector. The zero selector is used for
245 // cleanups, so slot zero corresponds to selector 1.
246 const std::vector<const GlobalValue *> &SelectorToFilter = MMI->getTypeInfos();
247
248 // Do a parallel iteration across typeids and clause labels, skipping filter
249 // clauses.
250 size_t NextClauseLabel = 0;
251 for (size_t I = 0, E = LPad->TypeIds.size(); I < E; ++I) {
252 // AddLandingPadInfo stores the clauses in reverse, but there is a FIXME
253 // to change that.
254 int Selector = LPad->TypeIds[E - I - 1];
255
256 // Ignore C++ filter clauses in SEH.
257 // FIXME: Implement cleanup clauses.
258 if (!isCatchEHSelector(Selector))
259 continue;
260
261 Asm->OutStreamer.EmitValue(Begin, 4);
262 Asm->OutStreamer.EmitValue(End, 4);
263 if (isCatchEHSelector(Selector)) {
264 assert(unsigned(Selector - 1) < SelectorToFilter.size());
265 const GlobalValue *TI = SelectorToFilter[Selector - 1];
266 if (TI) // Emit the filter function pointer.
267 Asm->OutStreamer.EmitValue(createImageRel32(Asm->getSymbol(TI)), 4);
268 else // Otherwise, this is a "catch i8* null", or catch all.
269 Asm->OutStreamer.EmitIntValue(1, 4);
270 }
271 MCSymbol *ClauseLabel = LPad->ClauseLabels[NextClauseLabel++];
272 Asm->OutStreamer.EmitValue(createImageRel32(ClauseLabel), 4);
273 }
274 }
275 }
276
emitCXXFrameHandler3Table(const MachineFunction * MF)277 void Win64Exception::emitCXXFrameHandler3Table(const MachineFunction *MF) {
278 const Function *F = MF->getFunction();
279 const Function *ParentF = MMI->getWinEHParent(F);
280 auto &OS = Asm->OutStreamer;
281 WinEHFuncInfo &FuncInfo = MMI->getWinEHFuncInfo(ParentF);
282
283 StringRef ParentLinkageName =
284 GlobalValue::getRealLinkageName(ParentF->getName());
285
286 MCSymbol *FuncInfoXData =
287 Asm->OutContext.GetOrCreateSymbol(Twine("$cppxdata$", ParentLinkageName));
288 OS.EmitValue(createImageRel32(FuncInfoXData), 4);
289
290 // The Itanium LSDA table sorts similar landing pads together to simplify the
291 // actions table, but we don't need that.
292 SmallVector<const LandingPadInfo *, 64> LandingPads;
293 const std::vector<LandingPadInfo> &PadInfos = MMI->getLandingPads();
294 LandingPads.reserve(PadInfos.size());
295 for (const auto &LP : PadInfos)
296 LandingPads.push_back(&LP);
297
298 RangeMapType PadMap;
299 computePadMap(LandingPads, PadMap);
300
301 // The end label of the previous invoke or nounwind try-range.
302 MCSymbol *LastLabel = Asm->getFunctionBegin();
303
304 // Whether there is a potentially throwing instruction (currently this means
305 // an ordinary call) between the end of the previous try-range and now.
306 bool SawPotentiallyThrowing = false;
307
308 int LastEHState = -2;
309
310 // The parent function and the catch handlers contribute to the 'ip2state'
311 // table.
312 for (const auto &MBB : *MF) {
313 for (const auto &MI : MBB) {
314 if (!MI.isEHLabel()) {
315 if (MI.isCall())
316 SawPotentiallyThrowing |= !callToNoUnwindFunction(&MI);
317 continue;
318 }
319
320 // End of the previous try-range?
321 MCSymbol *BeginLabel = MI.getOperand(0).getMCSymbol();
322 if (BeginLabel == LastLabel)
323 SawPotentiallyThrowing = false;
324
325 // Beginning of a new try-range?
326 RangeMapType::const_iterator L = PadMap.find(BeginLabel);
327 if (L == PadMap.end())
328 // Nope, it was just some random label.
329 continue;
330
331 const PadRange &P = L->second;
332 const LandingPadInfo *LandingPad = LandingPads[P.PadIndex];
333 assert(BeginLabel == LandingPad->BeginLabels[P.RangeIndex] &&
334 "Inconsistent landing pad map!");
335
336 if (SawPotentiallyThrowing) {
337 FuncInfo.IPToStateList.push_back(std::make_pair(LastLabel, -1));
338 SawPotentiallyThrowing = false;
339 LastEHState = -1;
340 }
341
342 if (LandingPad->WinEHState != LastEHState)
343 FuncInfo.IPToStateList.push_back(
344 std::make_pair(BeginLabel, LandingPad->WinEHState));
345 LastEHState = LandingPad->WinEHState;
346 LastLabel = LandingPad->EndLabels[P.RangeIndex];
347 }
348 }
349
350 // Defer emission until we've visited the parent function and all the catch
351 // handlers. Cleanups don't contribute to the ip2state table yet, so don't
352 // count them.
353 if (ParentF != F && !FuncInfo.CatchHandlerMaxState.count(F))
354 return;
355 ++FuncInfo.NumIPToStateFuncsVisited;
356 if (FuncInfo.NumIPToStateFuncsVisited != FuncInfo.CatchHandlerMaxState.size())
357 return;
358
359 MCSymbol *UnwindMapXData = nullptr;
360 MCSymbol *TryBlockMapXData = nullptr;
361 MCSymbol *IPToStateXData = nullptr;
362 if (!FuncInfo.UnwindMap.empty())
363 UnwindMapXData = Asm->OutContext.GetOrCreateSymbol(
364 Twine("$stateUnwindMap$", ParentLinkageName));
365 if (!FuncInfo.TryBlockMap.empty())
366 TryBlockMapXData = Asm->OutContext.GetOrCreateSymbol(
367 Twine("$tryMap$", ParentLinkageName));
368 if (!FuncInfo.IPToStateList.empty())
369 IPToStateXData = Asm->OutContext.GetOrCreateSymbol(
370 Twine("$ip2state$", ParentLinkageName));
371
372 // FuncInfo {
373 // uint32_t MagicNumber
374 // int32_t MaxState;
375 // UnwindMapEntry *UnwindMap;
376 // uint32_t NumTryBlocks;
377 // TryBlockMapEntry *TryBlockMap;
378 // uint32_t IPMapEntries;
379 // IPToStateMapEntry *IPToStateMap;
380 // uint32_t UnwindHelp; // (x64/ARM only)
381 // ESTypeList *ESTypeList;
382 // int32_t EHFlags;
383 // }
384 // EHFlags & 1 -> Synchronous exceptions only, no async exceptions.
385 // EHFlags & 2 -> ???
386 // EHFlags & 4 -> The function is noexcept(true), unwinding can't continue.
387 OS.EmitLabel(FuncInfoXData);
388 OS.EmitIntValue(0x19930522, 4); // MagicNumber
389 OS.EmitIntValue(FuncInfo.UnwindMap.size(), 4); // MaxState
390 OS.EmitValue(createImageRel32(UnwindMapXData), 4); // UnwindMap
391 OS.EmitIntValue(FuncInfo.TryBlockMap.size(), 4); // NumTryBlocks
392 OS.EmitValue(createImageRel32(TryBlockMapXData), 4); // TryBlockMap
393 OS.EmitIntValue(FuncInfo.IPToStateList.size(), 4); // IPMapEntries
394 OS.EmitValue(createImageRel32(IPToStateXData), 4); // IPToStateMap
395 OS.EmitIntValue(FuncInfo.UnwindHelpFrameOffset, 4); // UnwindHelp
396 OS.EmitIntValue(0, 4); // ESTypeList
397 OS.EmitIntValue(1, 4); // EHFlags
398
399 // UnwindMapEntry {
400 // int32_t ToState;
401 // void (*Action)();
402 // };
403 if (UnwindMapXData) {
404 OS.EmitLabel(UnwindMapXData);
405 for (const WinEHUnwindMapEntry &UME : FuncInfo.UnwindMap) {
406 OS.EmitIntValue(UME.ToState, 4); // ToState
407 OS.EmitValue(createImageRel32(UME.Cleanup), 4); // Action
408 }
409 }
410
411 // TryBlockMap {
412 // int32_t TryLow;
413 // int32_t TryHigh;
414 // int32_t CatchHigh;
415 // int32_t NumCatches;
416 // HandlerType *HandlerArray;
417 // };
418 if (TryBlockMapXData) {
419 OS.EmitLabel(TryBlockMapXData);
420 SmallVector<MCSymbol *, 1> HandlerMaps;
421 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
422 WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
423 MCSymbol *HandlerMapXData = nullptr;
424
425 if (!TBME.HandlerArray.empty())
426 HandlerMapXData =
427 Asm->OutContext.GetOrCreateSymbol(Twine("$handlerMap$")
428 .concat(Twine(I))
429 .concat("$")
430 .concat(ParentLinkageName));
431
432 HandlerMaps.push_back(HandlerMapXData);
433
434 int CatchHigh = -1;
435 for (WinEHHandlerType &HT : TBME.HandlerArray)
436 CatchHigh =
437 std::max(CatchHigh, FuncInfo.CatchHandlerMaxState[HT.Handler]);
438
439 assert(TBME.TryLow <= TBME.TryHigh);
440 assert(CatchHigh > TBME.TryHigh);
441 OS.EmitIntValue(TBME.TryLow, 4); // TryLow
442 OS.EmitIntValue(TBME.TryHigh, 4); // TryHigh
443 OS.EmitIntValue(CatchHigh, 4); // CatchHigh
444 OS.EmitIntValue(TBME.HandlerArray.size(), 4); // NumCatches
445 OS.EmitValue(createImageRel32(HandlerMapXData), 4); // HandlerArray
446 }
447
448 for (size_t I = 0, E = FuncInfo.TryBlockMap.size(); I != E; ++I) {
449 WinEHTryBlockMapEntry &TBME = FuncInfo.TryBlockMap[I];
450 MCSymbol *HandlerMapXData = HandlerMaps[I];
451 if (!HandlerMapXData)
452 continue;
453 // HandlerType {
454 // int32_t Adjectives;
455 // TypeDescriptor *Type;
456 // int32_t CatchObjOffset;
457 // void (*Handler)();
458 // int32_t ParentFrameOffset; // x64 only
459 // };
460 OS.EmitLabel(HandlerMapXData);
461 for (const WinEHHandlerType &HT : TBME.HandlerArray) {
462 MCSymbol *ParentFrameOffset =
463 Asm->OutContext.getOrCreateParentFrameOffsetSymbol(
464 GlobalValue::getRealLinkageName(HT.Handler->getName()));
465 const MCSymbolRefExpr *ParentFrameOffsetRef = MCSymbolRefExpr::Create(
466 ParentFrameOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
467
468 // Get the frame escape label with the offset of the catch object. If
469 // the index is -1, then there is no catch object, and we should emit an
470 // offset of zero, indicating that no copy will occur.
471 const MCExpr *FrameAllocOffsetRef = nullptr;
472 if (HT.CatchObjRecoverIdx >= 0) {
473 MCSymbol *FrameAllocOffset =
474 Asm->OutContext.getOrCreateFrameAllocSymbol(
475 GlobalValue::getRealLinkageName(ParentF->getName()),
476 HT.CatchObjRecoverIdx);
477 FrameAllocOffsetRef = MCSymbolRefExpr::Create(
478 FrameAllocOffset, MCSymbolRefExpr::VK_None, Asm->OutContext);
479 } else {
480 FrameAllocOffsetRef = MCConstantExpr::Create(0, Asm->OutContext);
481 }
482
483 OS.EmitIntValue(HT.Adjectives, 4); // Adjectives
484 OS.EmitValue(createImageRel32(HT.TypeDescriptor), 4); // Type
485 OS.EmitValue(FrameAllocOffsetRef, 4); // CatchObjOffset
486 OS.EmitValue(createImageRel32(HT.Handler), 4); // Handler
487 OS.EmitValue(ParentFrameOffsetRef, 4); // ParentFrameOffset
488 }
489 }
490 }
491
492 // IPToStateMapEntry {
493 // void *IP;
494 // int32_t State;
495 // };
496 if (IPToStateXData) {
497 OS.EmitLabel(IPToStateXData);
498 for (auto &IPStatePair : FuncInfo.IPToStateList) {
499 OS.EmitValue(createImageRel32(IPStatePair.first), 4); // IP
500 OS.EmitIntValue(IPStatePair.second, 4); // State
501 }
502 }
503 }
504